Residents who witnessed the blast say the explosion was caused by a missile strike, which Pakistani officials deny.

Pakistani Information Minister Sheikh Rashid Ahmed told CNN that Rabia apparently died while working with explosives.

Another Pakistani official, Interior Minister Aftab Ahmad Khan Sherpao, said only that the explosion killed "five miscreants, including three foreigners," and injured two others. Authorities are examining the home, he said.

However, residents of North Waziristan say they saw a unmanned aerial vehicle fire a missile on the house, Pakistani journalist Salim Bokhari said. Also, a photo from the European Pressphoto Agency shows Pakistani villagers holding a piece of shrapnel.

When the photo is enlarged, English words are visible on the shrapnel.

A former intelligence analyst said the debris appears to be from a U.S. weapon, but CNN cannot confirm whether the shrapnel came from a U.S. missile or if it's related to the Wednesday blast. The analyst added that the photo seemed authentic and the shrapnel did not appear fake.

The U.S. government has yet to make an official statement about Rabia's death or the blast, but two U.S. intelligence officials described Rabia's death as a "significant blow to al Qaeda and its organization."

The Egyptian-born Rabia, who was in his 30s, served as the No. 3 man in al Qaeda, behind Osama bin Laden and Ayman al-Zawahiri, the officials said, adding that his responsibilities included external planning of terrorist acts. He replaced Abu Faraj al-Libbi, who was captured earlier this year, they said.

"He was a big fish in al Qaeda," Ahmed said.

Before his death Wednesday, Pakistani officials had been tracking him for more than a month, Ahmed said. He narrowly slipped away from authorities November 5 and was slightly wounded in the leg, Sherpao said.